This invention relates to catalysts. In accordance with one aspect, this invention relates to catalysts useful for the disproportionation of olefins. In a further aspect, this invention relates to a process for the conversion of olefins. In another aspect, the invention relates to a method for preparing catalysts.
The disproportionation, or metathesis, of olefins is a reaction in which one or more olefinic compounds are transformed into other olefins of different molecular weights. The disproportionation of an olefin with itself to produce an olefin of a higher molecular weight and an olefin of a lower molecular weight can also be referred to as self-disproportionation. For example, propylene can be disproportionated to ethylene and cis-, and trans-2-butene. Another type of disproportionation involves the cross-disproportionation of two different olefins to form still other olefins. An example would be the reaction of one molecule of 2-butene with one molecule of 3-hexene to produce two molecules of 2-pentene.
By the term "disproportionation" or "metathesis" throughout this specification is meant the conversion of the feed olefinic (or unsaturated) hydrocarbon to a mixture of olefinic (or unsaturated) hydrocarbons having different numbers of carbon atoms than the feed hydrocarbons.
Many catalysts have been developed for disproportionation. For example, those comprising inorganic oxide supports containing a catalytic amount of a metal or metal oxide have been employed widely for conversion of olefins. The present invention is based upon the discovery of a way to improve the activity of such catalysts.